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Port Fuel Injection (PFI) system in hybrid gasoline engines is frequently in cold condition due to use for electricity generation. Under cold condition, the fuel film forms on the intake port wall does not evaporate completely during the cycle, and the injected fuel spray impinges on it in the next cycle. In this paper, the process of fuel film formation under multi-cycle fuel injection condition is analysed by applying the Total Internal Reflection Laser Induced Fluorescence method. In addition, the particle size distribution of spray droplets was measured in quiescent conditions with Super High Spatial Resolution Photography method, which allows for whole spray imaging while maintaining the spatial resolution of small droplets. As a result, the fuel adhesion mass per injection increases as the critical Weber number increases with repeated fuel injections under quiescent conditions. Under cross flow conditions, fuel mass impinging on the wall is much smaller than under quiescent conditions. Accordingly, the fuel adhesion mass per injection is almost constant with repeated fuel injections because of the small increase in the critical Weber number. [ABSTRACT FROM AUTHOR]

In a spark-ignition engine with intake port fuel injection, fuel is sprayed into the intake port under flow conditions and atomized droplets flow into the cylinder, some of which adhere to the intake port wall and form a liquid film. The liquid film adhered to the intake port is a factor in combustion fluctuations due to cycle-to-cycle variations of the air-fuel mixture in the cylinder, as well as unburned hydrocarbons and soot emissions. In this study, a wind tunnel experimental apparatus simulated an intake port was constructed to understand the wall adhesion characteristics of fuel spray in the intake port during engine startup and cold startup conditions. Scattered light photography was used to observe fuel spray characteristics in static and flow conditions, and total internal reflection laser-induced fluorescence (TIR-LIF) was applied to analyze the wall adhesion characteristics of fuel sprays. As a result, in the static field, the spray interaction increased with increasing injection pressure, and the amount of wall adhesion increased. However, in a flow field, the spray follows the flow as the injection pressure increases, and the amount of adhesion decreases. [ABSTRACT FROM AUTHOR]